Anyone needing to create an app icon should immediately check out Michael Flarup's amazingly awesome template here: http://www.pixelresort.com/blog/app-icon-template/
It's got loads of great photoshop actions baked in, lots of textures and nice border types, highlights, etc., and has save actions to save out every iOS icon size you'll need all at once, saving a TON of time.
We used it to create ours and couldn't be happier with how it's turned out.
Some other great icons made with this template can be seen in this Flickr group: http://www.flickr.com/groups/1873804@N25/pool/
Let us know what you make with it!